Chemical removal of an acid-soluble metal part in a deep well



Feb 17, 1948. P. H. CARDWELL x-:T AL 2436,196

CHEMICAL REMOVAL OF AN ACID-SOLUBLE METAL PART IN A DEEP WELL Filed Aug. 6, 1945 INVENTORS /OOU//f C0ra/We// By Lou/'s H E//ers ATTORNEKS Patented Feb. 17, 1948 UNlTl-io Isfr-A1' c 2,436,196 CHEMICAL aEMovALoF AN Aem-someta METAL PART IN A DEEP WELL raulfn. cuua'weu `una Louis H." liners,- rules,

Okla., assignors pany, Midland, Mich.

Ware,

toThe Dow ,Chemical Coma corporation of Dela- L mucatii". August 6 1945QSerial Netstazsfl 4 claims. v(01. 25a-855)' f "he invention relates to, thechemical removal or ali acid-solublemetal Vpartj in a deep well. Itv more particularly `":liiiceiils `anirnproved method of completing wells traversing ia* plurality ofv strata, in which a chemically?sll'lblcasingsec-` tion located opposite aselectedfstratumis res' moved by chemical action topermit iluidilow be-Y tween tile` well coreano the stratum. y

ln the usual yWeil completinin which a chem; ioally soluble section is included in Vthe casing` :stringl opposite a productive sone, the soluble seo'- tion is made ofaluminuin or anaiuxninum alloy, and its removal is effected by prolonged treatment with a quantity-of hydrochloric acid." i

A disadvantaged this-metrica which limits its usefulness 'murat-the action'ci the' acid 1s quite slew, so thatau ,inordinate amount of ,tlmeis ,onsuiiied in the operation aiidcom'plete removal is somewhat uncertain. 5" "I, i Y i particular objectY of theinv'eiiti'onis to proc' vide an improved method of, and composition for, chemically dissolviugrenleluminumlor aluminum alloy part, suchas a Acasing section, in the bore of a Well whereby cdmpleterapid removal is achieved. Other objects and advantages 'will betion 3. variouslaluminum-base alloys are suitable for' thepurposeas, ,for example,j`one containing about .1 percent .ofosilicomabout 1 percent of magnesium, and about 0.3 per cent oil chromium,

., the balance being valulninm'rfl; If desired, unalloyed aluminuminay 'be used The aluminum or los aluminum alloy section isfplaced in the casing string so that thesectionis opposite a productive zone. 4, the annular spaoebetween the casing stringand the well hole beinglled with cement 5... Such Well construction isy conventional and forms nopart'bf'theinvention. A Y

4in preparing the ell for treatment sro as to. remove thefsolublefsection 3 according 4to the in-A vention, the portion of the Wellbelow the productive zone '4 isbridged as with a `filler 6, and a packer 1 is Set in, the casing at the top of the zone therebyV to isolate "for treatment the portion of the `Well containing `the soluble section. The

packer is provided with a central passage for admitting the outer tube Bextending from the top come apparent as the description of tlieinvertiii proceeds. A 4

According tothe invention` dissolution of c parts or eouipment made or alumiiium'pr aluminum alloy m the well is achieved by subjecting the metal part to the corrodingactionvof @hydrochloric acid solution to which has been added au aliphatic carboxylic acidfsufcl'l` `as acetic;airline` acetic (glycine), citric, gluclmic;lactic,V ol'ialic, and tartaric.: To prevent or reduce attack by the acid solution on adjacent jferrous metal iparts, ,when such are present, in inhibitor` of such action may-be 'in-r eluded in theecldselutlcn;

" between thetop of The invention`may morereadily understood fromthe following` detailed description and 'accompanying 1dravtfin'gfoi a Amildev '0f all'yig Out the invention, such mode illustrating butone of various ways inwhich the principleof the inten#- tion may be used-J" the'saiddrawing the .single ligure illustrates schematijoallyinvertical section an oil well'in whichjan acid-'soluble seotionio- Vcated in the casingstring opposite `a product iye zoneis being removed chemically; 4

@Sterling more partielilerlr tohferewie, the well bore I is provided witha. Acasing stringV 2l con-j `tion 3 of the casing,

ofthe Well to just belowthe packer. yAn inner tube 9 is Strungthroughthe outer'tube and extends from the top ofthe wellto near the bottom of the soluble section. A

After arranging the apparatus as described, the chemical solvent. cfr-,hydrochloric acid to which V'aliphatic carboxylic acid miiiay'a be introduced throughtube 9 so as to fill the space I0 in the cased portion of the well thef bridgeV 6 and the bottom ofthe tube As the chemical solvent becomes spent by dissolvingthegmetal of the soluble secl`fresh solvent may be introduced, if necessary,:thereby displacing the spent solution from the Vwelltlfirough-tube -8. Itis preferableto continuously circulate thechernical solvent into the space vIll through tube 9jwhi1e the spenti or partilly spent solventfsolution is displaced through jtubey 8; The amount of solvent ito employ depends upon the concentrationof HC1 therein and the weight of the aluminumV section to be removed, and `nia'y be computed on the basis of the known stoichiometrical relationship between lHC1 and aluminum tol form aluminum chloride '(AlCle). For example, v approximately 1.7 gallons of 25 percent hydrochloric acid solution is re- K quired per pound of aluminuln'section. Various taining an aluminum alloy (alll-SglliblVseo concentrations of HC1 may be used,l suohas l5 to :35 per cent, concentrationbetween about 20 and 'pe'r centibeingpeferrd 3 A suitable amount of one of the aforementioned aliphatic carboxylic acids to use in the hydrochloric acid solution to increase its rate of attack on the acid-soluble section is between aboutV 0.1 and 3 per cent of the weight of the acid solution, between 0.5 and 1.0 being generally preferred.

In order to reduce or preventattack by the acid on the ferrous metal parts of the well which may be exposed to the` acidsolution..particularlythc. steel casing adjacent-tto the acid-solublegpart to be removed, any of the well known corrosion inhibitors may be used, such as a soluble-arsenic,

compound, e. g., the arsenate or arsenite of sodium, organic sulfur compounds, such. as. the-.increr captans, organic nitrogen bases, etc., in itheus'uall I small quantities such as 0.4 to. 1.0 per centof the weight of the acid solution. y

As the aluminum section of the of heat oi neutralization and hydrogen is evolved which is allowed to escape throughv pipe 185 Thecasing dissolves, u the solution becomes heated due to the liberation 4 TABLE II Reaction rate of hydrochloric acid solutions on aluminum alloy accelerated by oalic acid Temperature F.) of Reacting Materials After- Composition of Acid Solution Min. Min. Min. Min. Mn.

HC1a1`one. se v5108" 162 .220 22o 20%+0.5% Oxalic.. 86 110 220 220 216 20 44.0% oxalic.- 86 116 220 220 218 HC1 alone se 159 22s 221 221 25%+0.5% 0Xalic 86 166 224 228 226 25%=l=1.0%0xa1c 86 202 226 226 226 .The data inthe; tables show that by adding 'fan'r aliphatic-carboxylic acid in relatively small generation of heat is an advantage asiit. speeds.

subjected to thedissolving action of hydrochloric;

acid solution to which various aluminum corrosion accelerators` were added; In conducting these tests 300cc., lots of acidi were placed in a calorimetertogether withv a piece of' an aluminum alloy containing'0.2per Vcent Copper, v1'-'1.ier cent magnesium, 0.4 per cent silicon, 0279er cent chromium, the. balance being aluminum,y andthe rate of dissolvingfofl the aluminum alloy deter'- mined by observing from time to. time the temperature attained bythe reacting` materials. In; these tests the higher thetemperature attainedV by the materials ina given time thefaster the dissolving of the aluminum alloy occurred.

Tables I and II present data so'fobtaine'd.l

o TABLE'I" Rate of reaction of 15% hydrochloric. acid solution on aluminum alloy accelerated by aliphatic carboxylic acid Temperature .(F.) oiReacting Concentration and Kind oi Materials After* Aluminum Corrosion Accelerator Q 1.5 45. 60

Min M111 Min. Min. Min.

None .(Blank) 86, 106y 121` 135 149 1.0% Acet'ic Ac 86 114 138 166 205 1.9% Citrlc Acid 86 105 132 160 185 1.0%G1uc'nicAcid '86 109 122 142 i 173 0.525% Glycine 86. 109. 142 n 173 211 1.0% Glycine. 86 108' l127 150 173 0.25% Lactic Acid 86- 118 138 179 212 0.5% L'actic Acid 86 117 152 210 214 1.0% I actie Acid s6 117 151 212 214 3.0% lactic Acid 86 108 122 '134 v 148 0.25% O xa'flicAoid 86 118 152 207 214 0.5% Oxalic Acid. 86 117 155 213 214 1.0% 'oxanc Acids6 119 152 214 214 r3,0%Oxa1ic Acid 86 112` 136 175 212 0.10% Tartaljic Ac `86 11'1 140 171 21'2 0.15% Tartari'c Acid 86 f 110 -147 1 189 214 y0.25% Tartaric Acid. 86 132 200 214 Y 213 0.5% Tartaric Acid.; 86- 125 158v '214 214 j1 0'72, TartarlcvA'cid.. :86 T124 i 4156V 210 v v214 3.0% Tartarric Acid.- f 86 128 162 185 amount'. to .hydrochloric acid solution its rate of attack on aluminum alloy is increased. This is evident fromthe fact that the temperature of V'the reacting materials attains a higher value in less time when an aliphatic carboxylic acid is present in the acid solution.

' As aiurther example of the increased speed of,` action obtainable with our acid solution com,-

Parative tests were made inwhich a given weight oi?4 the acid solution was allowed toexpend itselfin dissolving aluminum alloy tubing.. the alloy.- having the composition last mentioned.. these; tests, it was found Athat whereas commercial hyz drochloric acid alone containing 25-per cent by' weight of HC1.. expended itself `i n,abou t 30 minutes, the additionY of from 0-.5 per. centxto 1- per cent of oxalic acid to the same,hydrocliloricv acidAv solution increasedits rate. of actionl so that-onlyl about-20 minutes were required for. its expendif ture under comparable conditions. Similar tests.- madewith'20 p er cent hydrochloric acid-solution gavea spending timev of 45. minutes when used.

aloneincomparison with a spending time of about125 to v'30 minutes when thevfsame concen-l tration of acid solution containing from 0.5 vto lper cent of oxalic. acid, respectively, was used similarly. y Y

Theterm aluminum used herein and the appended claims is used to mean all grades of aluminumvmetal,4 and the term aluminum alloy means alloys ,of aluminum containing at leastv about per cent of aluminum.

We claim:

1. The lmethod of removingV from a Wella metal part formed of aluminum. and its alloys which comprises subjecting the part tothe dissolving action of an aqueous solution. containing from about 20. to 30 per cent of hydrochloric acid and 0.25. t03 percent of oxalic acid and an inhibitor of the action ofthe hydrochloric acid on ferrous xAneta'l;` I

2. The method of removing irom a well a metal part formed of aluminum and its. alloys Whichcomprises subjecting theQpart. tothe dissolving action of an aqueoussolution containing from about 20`to 30 percentof. hydrochloric acid and"- 0.25 to 3 per cent of' lactic acid and an inhibitor.4

of the action of the hydrochloric acid, on ferrous metal. Y

3. The method of removing'jfrom a well a metal -part formed of aluminumfand its alloys which of the action of the hydrochloric acid on ferrous..

metal. l

4. The method of removing from a well a. metal part formed of aluminum and its alloys which comprises subjecting the part to the dissolving action of an aqueous solution containing from about 15 to 35 per cent of HC1, about 0.25 to 3 per cent of an aliphatic carboxylic acid selected from the group consisting of lactic acid, oxalic acid and tartaric acid, an an inhibitor of the action of the hydrochloric acid on ferrous metal.

PAUL H. CARDWELL. LOUIS H. EILERS.

REFERENCES CITED The following references are of record in the 111e of this patent:

Number UNITED STATES PATENTS Name Date Chamberlain I Dec. 17, 1935 Morgan Aug. 23, 1938 Bresler Dec. 13, 1938. Stoesser Oct. 3, 1939 Fry Oct.l 15, 1940 Chamberlain II Feb. 25, 1941 Zacher Mar. 11, 1941 Hall et al Aug. 19, 1941 Salnikov Nov. 4, 1941 Frye et al. Feb. 29, 1944 

